Aerial and vessel surveys conducted by the Provincetown Center for Coastal Studies on Wednesday documented about 90 right whales throughout Cape Cod Bay.

The animals are currently feeding just below the water's surface on high concentrations of zooplankton, making them incredibly difficult to see and putting them at risk for vessel collision, officials said.

The Division of Marine Fisheries is urging vessel operators to proceed with extreme caution, reduce speed (less than 10 knots) and post lookouts to avoid colliding with the highly endangered whales.

The North Atlantic right whale is one of the most endangered large whales in the world, with a population of approximately 550 animals. Right whales gather annually in the waters off of Cape Cod to feed.

Last year, about 50 percent of the known population was sighted in Massachusetts waters.